How about this: On the frontleft breast, the words: "Get off my back!" Onm the back, a full sized monkey grabbing the t-shirt with all four paws, looking over it's shoulder at whoever is behind the wearer, making an evil/mischeivious face. "I got a Monkkey on my back"...get it?

I imagine Pac-Man with huge teeth chasing down a scared blue ghost in a dark corridor. It could look like a scene from a horror movie.

I hate to admit, but I would love to see some Anime inspired shirts around here. Full Metal Alchemist will long have a place in my heart, and so does almost anything with alchemy as an underlying theme.

Sonic the hedgehog, and Sonic screw driver.

I was thinking..there's only really 2 guys in the Mario universe(excluding evil ones), yet there's 3 girls, so I think it'd be funny to have Peach hanging onto Mario, Daisy hanging onto Luigi, and then Rosetta from Mario Galaxy getting angry because there's only Toadstool left(or Rosetta hanging on Mario, since she is I'm sure considered prettier by some), possibly with the other characters(1 or more) specifically pointing to Toadstool with a sweatdrop or something.(indicating that Toadstool is the only choice left)